Recent increase in integration and capacity of large-scale integration (LSI) circuits require further miniaturization of semiconductor devices. In the lithography technique to form a desired circuit pattern on a semiconductor device, pattern transfer is performed using an original pattern referred to as a mask (reticle). To produce a high accuracy mask used in the pattern transfer, a charged particle beam drawing apparatus which has excellent resolution and uses an electron beam is used.
In the charged particle beam drawing apparatus, the charged particle beam is formed and deflected using a plurality of electrodes in a charged particle optical system, while a stage, on which an object such as a mask is supported, is moved, and the object is then irradiated with the obtained charged particle beam. Thus, a predetermined pattern is drawn on the object on the stage.
If, however, charging and contamination of the electrodes used in forming and deflecting such a charged particle beam occur, there arises a problem that a drawing accuracy is deteriorated. To solve this problem, ozone gas is supplied to the drawing apparatus for cleaning. The ozone gas is generated by an ozone generator and supplied to the drawing apparatus through a pipe.
The ozone generator, which generates the ozone gas, is configured to vibrate and generate a magnetic field. The generated vibration and magnetic field become factors to decrease a drawing accuracy of the drawing apparatus. Usually, therefore, the ozone generator is disposed at a position apart from the drawing apparatus far enough to ignore the decrease of the drawing accuracy due to the vibration and magnetic field. As a result, a longer pipe is needed to connect the ozone generator with the drawing apparatus. As the length of the pipe and stay-time of the ozone gas in the pipe become longer, the ozone gas is decomposed in the pipe and converted into oxygen. Thus, it has been difficult to supply a high concentration ozone gas to the drawing apparatus.